The Aquatic Commons is a thematic digital repository covering the natural marine, estuarine /brackish and fresh water environments . It includes all aspects of the science, technology, management and conservation of these environments, their organisms and resources, and the economic, sociological and legal aspects.
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Mostrando recursos 1 - 20 de 359
Invertebrate communitites of lakes Mutanda, Mulehe, Kayumbu and Chahafi and their role in fishery production - Ndawula, L.M.; Kiggundu, V.
Kisoro is a small district (734 km2 ) located in the highland areas of south western Uganda; bordering with Rwanda in the south, Democratic Republic of Congo in the west and Kabale District in the north and the east. The district contains four medium- to- small lakes namely: Mutanda (26.4 km2 ), Mulehe (4.1 km\ Kayumbu (2.2 km2) and Chahafi 1.0 km2). These lakes support small subsistence fisheries for a largely agricultural local population. They are, therefore, locally important as a source of animal (fish) protein, income and employment to the riparian human communities. The fish species include tilapiine fishes:...
Economic impacts of globalisation at the district, landing site and sub-sector enterprise levels on Lakes Kyoga, Albert and Victoria - Odongkara, K.; Wegoye, J.; Kyangwa, M.; Nyapendi, A.
The Globalisation and fish utilisation and marketing study is a collaboration between the Fisheries Resources Research Institute (FIRRI) and the Mike Dillon Associates Limited , with funding from the Department for International Development (DFID) of the Government of the United Kingdom. The study is designed to examine the impact of the development of the export fishery on the fish producers, processors, traders and consumers in the artisanal fishery in Uganda. FIRRI 's role is to collect field data relating to the livelihoods of artisanal fish producers, processors, traders and consumers. in particular data relating to income and revenue flow. The...
Global commodity chains and the development of poor fisherfolk in Uganda - Marriott, A.
The Ugandan fishery, heavily influenced by the emergence of global markets, is extremely dynamic. In recent years a major export trade, principally in Nile perch fillets from Lake Victoria, has expanded markedly. The growth of this factory based processing industry has had a marked impact on the pre-existing artisanal fishery, which has become increasingly dependent on supplying the export market instead of its traditional local small-scale markets. The industrial fishery developed as a response to the liberalisation of the management of the Ugandan economy and the consequent opening up of the export markets in North America and Europe. The emergence...
The impact of fishing gears and methods: with recommendations for management of the fisheries of Lakes Victoria, Kyoga and Nabugabo - Ogutu-Ohwayo, R.; Twongo, T.K.; Wandera, S.B.; Balirwa, J.S.
Historical analysis has shown that use of destructive fishing gears and methods contributed much to the initial depletion of fish stocks from Lakes Victoria and Kyoga. From about 1930 to 1960, the fisheries of Lake Victoria were managed by controlling the mesh size of gill nets. Gill net s of less than 127 mm (5) stretched mesh had been prohibited on Lake Victoria because they cropped immature Oreochromis esculentus (Ngege) which were at that time the most important commercial species. When the mesh size restriction was repealed in the Ugandan, Tanzanian and Kenya, there was a shift to smaller meshes...
Trophic interrelationships and food-webs among the fishes in ecosystems of the Victoria and Kyoga lake basin - Mbabazi, D.; Ogutu-Ohwayo, R.; Wandera, S.B.; Namulemo, G.
The Victoria and Kyoga lake basins had a high fish species diversity with many fish species
that were found only in these lakes. Two Tilapiines species Oreochromis esculentus and
Oreochromis variabilis were the most important commercial species in these lakes and were
found nowhere else on earth except in the Victoria and Kyoga lake basins (Graham 1929,
Worthington 1929). Lakes Kyoga and Nabugabo also had endemic haplochromine species
(Worthington 1929, Trewavas 1933, Greenwood 1965, 1966). As stocks of introduced
species increased, stocks of most of the native species declined rapidly or disappeared
altogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, some
The role of Yssichromis species (Pisces: Cichlidae) in the trophic ecology and foodwebs of Lake Victoria - Ebong, I.; Wandera, S.B.; Ogutu-Ohwayo, R.
Many haplochromine cichlids coexisted in Lake Victoria before the upsurge of Nile
perch. The introduction of the Nile perch led to depletion of many haplochromines and
other fish species in Lake Victoria. The impact of Nile perch predation on
haplochromines differed for different haplochromine trophic groups. Yssichromis
fusiformis (G) and Yssichromis laparogramma (G) are among the species that have
survived in the lake. Yssichromis spp. was studied with the aim of determining their
trophic role, food and feeding habits. Samples were collected from Bugaia, Buvuma
channel and Napoleon Gulf in the northern part of Lake Victoria. The food of
Yssichromis spp. varied with size of fish. Both Y...
Changes in fish fauna and the impact of the introductions on fish yield - Ogutu-Ohwayo, R.
There have been considerable changes in fish species
composition in Lakes victoria, Kyoga and Nabugabo since the Nile perch were introduced. Populations of most of the native species have declined and many species may have become extinct. The original decline in the fish stocks was due to overfishing but the recent and more drastic decline has been attributed to predation by the Nile perch. Nile perch feeds on invertebrates changing to a piscivorous diet with size. Haplochromine cichlids, which were the
most abundant fish in Lakes Victoria just before the Nile perch populations started increasing rapidly have been depleted. As more suitable...
The biology and ecology of native non-cichlids in the Victoria and Kyoga lake basins - Mbabazi, D.; Ogutu-Ohwayo, R.; Wandera, S.B.; Namulemo, G.
An overview of the biology and ecology of some of the constantly less important
commercial species is given below. These included Bagrus docmac, Clarias gariepinus,
Protopterus aethiopicus, Labeo victorianus, Barbus spp, Mormyrids, Synodontis spp, and
Schilbe intermedius. The stocks of most of these species declined due to over-exploitation
and introduction of non-native fishes especially Nile perch. A few of these taxa still survive
in the main lake and others in satellite lakes. The current status of these species in the
Victoria lake basin is not known but the available information provided some information
on some habitat and other requirements of some of these originally important species of...
The biology, ecology, distribution and conservation of some surviving native non-cichlid fish species of Lakes Victoria, Kyoga and Nabugabo - Olowo, J.P.; Ogutu-Ohwayo, R.
Prior to introduction of non-native fish species into Lakes Victor i a, Kyoga and Nabugabo, the three lakes suppor ted diverse fish fauna representing 13 families consisting of six cichlid genera and fifteen non-cichlid genera. There were about 50 non-cichlid species and over 300 cichlids consisting of mainly haplochromines (Graham 1929, worthington 1929, Greenwood 1960). Many of the species were commercially and scientifically important and provided a rich variety of protein source to choose from. Following introduction of the Nile perch and several tilapiines species, most of the native species were drastically reduced and some have apparently disappeared. The few...
The biology, ecology and the fishery of Mukene, Rastrineobola argentea in Lakes Victoria, Kyoga and Nabugabo - Wandera, S.B.
Rastrineobola argentea, local name.s Mukene (Uganda) Omena (Kenya) and Dagaa (Tanzania) occurs in lakes Victoria, Kyoga and Nabugabo (Greenwood 1966). Until the decline of the native fishes especially the haplochromines, R. argentea was of little economic importance to the fisheries of these lakes. The stocks of this species have now increased and commercial catches on Lake Victoria account for over 30%. Fishing for R. argentea is currently still restricted to inshore areas and within the fringing islands of Lake Victoria. This fishery is not yet established on Lakes Kyoga and Nabugabo although the species is quite abundant in these lakes...
Biology, ecology and the fishery of Mukene, Rastrineobola argentea - Wandera, S.B.
Food and feeding, condition factor, breeding periods, growth and size at first maturity of
a small pelagic cyprinid Rastrineobola argentea (P.) in Lake Victoria are determined.
Fishing gears and methods that have been used in the exploitation of the species and
could be harmful to the fishery are outlined. Management measures leading to possible
sustainable exploitation of the fishery are suggested.
Adult R. argentea feed on zooplankton during daytime. Juveniles feed on planktonic
early instars of lakefly larvae. Although the species breeds throughout the year, two
breeding peaks were observed during the drier months of August and December January.
Least breeding was observed in the rainy months of...
The biology, ecology and impact of the Nile perch, Lates niloticus in lakes Victoria, Kyoga and Nabugabo and the future of the fisheries - Ogutu-Ohwayo, R.
Nile perch (Mputa), Lates niloticus was introduced into Lakes Victoria and Kyoga from lake Albert to increase fish production of these lakes by feeding on and converting the small sized haplochromines (Nkejje) which were abundant in these lakes into a larger table fish. It was, however, feared that Nile perch would prey on and deplete stocks of the native fishes and affect fish species diversity. Nile perch became well established and is currently among the three most important commercial species. It is presently the most important export fish commodity from Uganda. Considerable changes have taken place in fishery yield, and...
The biology, ecology, distribution and conservation of surviving haplochromine cichlids in Lakes Victoria, Kyoga and Nabugabo - Namulemo, G.; Wandera, S.B.
Haplochrmine cichlids were the most abundant taxa in Lakes Victoria, Kyoga and Nabugabo prior to introduction of the Nile perch. As stocks of the introduced predator increased, these taxa were depleted to such an extent that they are now virtually absent from the lake.
The haplochromine cichlids played an important role in the ecology of Lakes Victoria, Kyoga and Nabugabo. They occupied virtually all trophic levels in the lake and facilitated an efficient flow of energy through the ecosystem. Their depletion seem to have left much organic matter whose decomposition has contributed to accumulation of dead organic matter which may be...
The biology and ecology of the Nile perch, Lates niloticus, and the future of its fishery in Lakes Victoria, Kyoga and Nabugabo - Ogutu-Ohwayo, R.
Lakes Victoria, Kyoga and Nabugabo had a similar native fish fauna of high species diversity. stocks of most of the native species declined rapidly and some completely disappeared after Nile perch was introduced and became well established. Although, overexploitation
of the fish stocks, competition between introduced and native tilapiines and environmental degradation contributed to the reduction in fish stocks, predation by the Nile perch has contributed much to the recent drastic reductions in fish stock and could even drive the stocks to a total collapse. Nile perch is also currently the most important commercial species in Lakes victoria, Kyoga and Nabugabo...
The biology, ecology, population parameters and the fishery of the Nile tilapia, Oreochromis niloticus (L) - Balirwa, J.S.
Oreochromis niloticus (the Nile tilapia) and three other
ti1apine species: Oreochromis leucostictus, Tilapia zi11ii and T.
rendallii were introduced into Lakes Victoria, Kyoga and Nabugabo in 1950s and 1960s. The source and foci of the stockings are given
by Welcomme (1966) but the origin of the stocked species was Lake
Albert. The Nile tilapia was introduced as a management measure to
relieve fishing pressure on the endemic tiapiines and, since it
grows to a bigger size, to encourage a return to the use of larger
mesh gill nets. Ti1apia zillii was introduced to fill a vacant
,niche of macrophytes which could not be utilised' by the other tilapiines....
Genetic status of selected fish taxa in relation to conservation of genetic and species diversity in the Victoria and Kyoga Lake basins - Mwanja, W.
Cichlids are known for their explosive radiation especially in the African Great Lakes marked with a high level of lake endemism. These fishes have been characterized mainly along trophic and habitat differences, by variation in morphological structures such as teeth and jaws and by differences in body shape and coloration. Cichlids are important as a microcosm of macroevolution. The explosive radiation, young evolutionary scale, and the isolation of groups characterized with high levels of endemism and presence of living fossils makes the group important for evolutionary and genetic studies. Lake Victoria region cichlids which are isolated and relatively more recent...
Characterization of genetic biodiversity of Nile perch, Lates niloticus, Tilapiines, Haplochromine flock and Ningu (Labeo victorianus) in the Victoria Lake Basin: an overview - Mwanja, W; Ogutu-Ohwayo, R.
Genetic biodiversity is the vaflatlOn among individuals within and between units of interbreeding individuals (populations) of a species. It includes inheritable and transmittable differences that occur between individuals andlor popuhitions of a given species through reproductive interaction. There exists enormous variability among individuals andlor populations of a species for most living organisms, and most of this variation is inheritable. differences among individuals arise through mutation and via recombination of genes during meiosis. These ifferences are then transmitted to successive generations through sexual reproduction and maintained in the populations through processes such as natural selection and genetic drift. Unfortunately much of...
The diversity of amphibians, reptiles and mammals and their importance in the Victoria and Kyoga lake basins - Behangana, M
The shore margins of Lakes in the Victoria basin are highly dented and mostly swampy, fringed by Papyrus and other wetland vegetation types important habitats for herpetofauna and wetland adapted mammals. Of recent, the extent of the 'wetland' has been extended in several places by the Water Hyacinth (Eichornia cryaseps).
Ecologically, amphibians are important in many ways; they are mostly predators, acting as primary and secondary carnivores. Their prey consists mostly of insects, some of which are pests to crops or disease vectors. They are also inter-inked in food chains, often acting as food for other vertebrates, such as pigs, birds,...